Platelet is a minute, irregularly shaped, disklike cytoplasmic body found in blood plasma that promotes blood clotting and has no definite nucleus, no DNA, and no hemoglobin.

• 白细胞分多种，如嗜中性粒细胞、淋巴细胞、嗜酸性细胞、单核细胞和嗜碱粒细胞等。